For preparing olefin (co)polymers such as an ethylene homopolymer, an ethylene-.alpha.-olefin copolymer, a propylene homopolymer and a propylene-.alpha.-olefin copolymer, processes of polymerizing olefins in the presence of a Ziegler catalyst comprising a titanium compound and an organoaluminum compound or a vanadium catalyst comprising a vanadium compound and an organoaluminum compound are conventionally known.
Also known are processes of polymerizing olefins in the presence of a metallocene catalyst comprising a transition metal compound such as zirconocene and an organoaluminum oxy compound (aluminoxane), and it is known that the use of the metallocene catalyst makes it possible to polymerize olefins with high activities and to obtain olefin (co)polymers of narrow molecular weight distribution and narrow composition distribution.
Recently, the requirements for properties of the olefin (co)polymers have varied, and olefin (co)polymers of various properties have been desired. Moreover, development of a transition metal compound catalyst component capable of producing such olefin (co)polymers is also desired.
Under the circumstances, Japanese Laid-Open Publication No. 345793/1993 discloses a novel transition metal compound having an indenyl group and a fluorenyl group as ligands serving as an olefin polymerization catalyst component. However, in polymerization of an olefin using this transition metal compound as a catalyst component, the polymerization activity is low so that only a polymer of low molecular weight is produced.
EP0707016A1 also discloses a transition metal compound having an indenyl group and a fluorenyl group and a catalyst in which a specific aryl group such as a phenyl group or a naphthyl group is introduced into a specific position (4-position) of the indenyl group. However, in polymerization of an olefin using this transition metal compound as a catalyst component, the polymerization activity is also low so that only a polymer of low molecular weight is produced.
The present inventors have studied under such circumstances as mentioned above, and as a result they have found that by the use of a compound wherein a specific substituent is introduced at the specific position of the indenyl group in the above-mentioned transition metal compound, an olefin (co)polymer of high molecular weight can be prepared with high polymerization activities and an olefin copolymer of high comonomer content can be obtained. Further, the present inventors have also found that an olefin (co)polymer of high molecular weight can be prepared with much higher polymerization activities and an olefin copolymer of much higher comonomer content can be obtained by introducing a specific substituent at the specific position of the fluorlenyl group of the characteristic transition metal compound. Thus, the present invention has been accomplished.